A. Choose the correct answer
_____ 1. Equilibrium is characterized by
a. opposing processes occurring at equal rates.
b. an open system.
c. net change in the amount of substance in one phase.
d. changes in physical states.
_____ 2. The process of changing from a solid to a gas is known as
a. condensation.
b. sublimation.
c. deposition.
d. vaporization.
_____ 3. Which of the following liquids is most volatile?
a. water
b. ether
c. molten salt
d. skim milk
_____ 4. A phase is defined as any part of a system that has
a. the same composition throughout.
b. the same properties throughout.
c. the same properties and composition throughout.
d. the same temperature throughout.
_____ 5. Dry ice sublimes into carbon dioxide gas. If the proper conditions are maintained and the
system is closed, the dry ice and the carbon dioxide gas will eventually
a. become the same phase.
b. reach equilibrium.
c. stop changing phase.
d. Both (a) and (b)
_____ 6. If the vapor pressure of water is 4.25 kPa at 30.0C, the vapor pressure of water at 10.0C is
most likely to be
a. 0 kPa.
b. 1.23 kPa.
c. 4.25 kPa.
d. 12.34 kPa.
_____ 7. The temperature at which the vapor pressure of a substance equals atmospheric pressure is its
a. boiling point.
b. critical point.
c. melting point.
d. triple point.
_____ 8. The amount of energy needed to melt one mole of a substance is its molar
a. enthalpy of fusion.
b. enthalpy of vaporization.
c. entropy of fusion.
d. entropy of vaporization.
_____ 9. The point on a phase diagram that indicates the temperature and pressure conditions at which
the solid, liquid, and vapor of the substance can coexist at equilibrium is known as the
a. critical point.
b. phase point.
c. triple point.
d. equilibrium point.
_____ 10. Assume you have a substance that plots right on the liquid-vapor equilibrium line on its
phase diagram. If you raise the temperature slightly and keep the same pressure, the
substance will now be
a. a solid.
b. a liquid.
c. a gas.
d. on a different equilibrium line.
_____ 11. What is the approximate angle between two hydrogen-oxygen bonds in water?
a. 90
b. 102
c. 105
d. 120
_____ 12. The bond between oxygen and hydrogen in a water molecule is
a. ionic.
b. hydrogen.
c. polar-covalent.
d. dipole-dipole.
_____ 13. The molecular geometry of a water molecule is
a. linear.
b. bent.
c. trigonal planar.
d. triangular.
_____ 14. Liquid water forms molecular groups. How many molecules of water are there in each
group?
a. one to two
b. two to four
c. three to six
d. four to eight
_____ 15. If water molecules were not linked by hydrogen bonds to form groups in liquid water, what
would be the physical state of water at room temperature?
a. solid
b. liquid
c. gas
d. a mixture of liquid and gas.
___16.What is the reason for the relatively low density of ice?
a. empty spaces between molecules
b. the high number of hydrogen bonds
c. the small size of hydrogen and oxygen atoms
d. the low molar mass of water
_____ 17. Compared with nonpolar substances of comparable molecular mass, water’s molar enthalpy
of vaporization is
a. higher.
b. lower.
c. similar.
d. equal.
_____ 18. Water’s relatively high boiling point is the result of
a. covalent bonding.
b. hydrogen bonding.
c. ionic bonding.
d. London forces.
_____ 19. The molar enthalpy of fusion of ice is
a. equal to the enthalpy of many other solids.
b. approximately the same as the enthalpy of many other solids.
c. larger than the enthalpy of many other solids.
d. smaller than the enthalpy of many other solids.
_____ 20. Compared with the boiling point of nonpolar substances of comparable molar mass at 1 atm,
the boiling point of water at 1 atm is
a. higher.
b. lower.
c. equal.
d. approximately the same.
B. Match the letter on the diagram with the term for that point or region.: (8 Marks)
Phase Diagram for H2O
1. ______ Critical point
2. ______ Vapor
3. ______ Normal freezing point
4. ______ Triple point
5. ______ Solid
6. ______ Normal boiling point
7. ______ Liquid
8. ______ Critical pressure